The use of composite catalysts utilizing a natural or synthetic zeolite as one component are well known in the art for catalytic cracking and hydrotreating processes such as hydrocracking. U.S. Pat. No. 3,558,475 to Jaffe, for example, teaches the use of a catalyst comprising a silica-alumina gel component containing a Group VI hydrogenation component such as Mo or W plus a Group VIII hydrogenation component such as nickel and wherein from 30 to 70 weight percent of a zeolite molecular sieve component free of catalytic metals is dispersed through the gel matrix for the hydrotreating of hydrocarbon charge stocks. Jaffe's catalyst must have at least 15 weight percent silica. A later patent (U.S. Pat. No. 3,598,719 to R. J. White) teaches the use of substantially the same catalyst as Jaffe except the silica content is less than 15 percent (thus pure alumina could be used) for hydrotreating with special emphasis on the high hydrocracking and hydrodenitrification properties of the catalyst with low fouling (good aging).
Improved catalysts for hydrocracking of hydrocarbon charge stocks especially in the presence of nitrogen, e.g., shale oils, are continuously being sought. Further, in some instances it is desirable to hydrocrack the charge stocks to produce higher yields of product which is lower in boiling range than the feedstock, but which contains a favorably high ratio of higher boiling to lower boiling products. For example, hydrocracking of a heavy gas oil to maximize middle distillate rather than gasoline, or hydrocracking a furnace oil to maximize naphtha rather than C.sub.4 and lighter gases.